Enhanced Visible Light Photocatalytic Activity of N and Ag Doped and Co-Doped TiO2 Synthesized by Using an In-Situ Solvothermal Method for Gas Phase Ammonia Removal

Abstract

Single doping and co-doping of N and Ag on TiO2 were successfully prepared by using an in-situ solvothermal method and their structural properties and chemical compositions were characterized. The results indicated that all photocatalysts displayed in TiO2 anatase crystal phase, and a small mesoporous structure was observed in the doped materials. The main roles of N and Ag on the property and photocatalytic activity of TiO2 were different. The N doping has significantly enhanced homogenous surface morphology and specific surface area of the photocatalyst. While Ag doping was narrowing the band gap energy, extending light absorption toward a visible region by surface plasmon resonance as well as delaying the recombination rate of electron and hole of TiO2. The existence of N in TiO2 lattice was observed in two structural linkages such as substitutional nitrogen (Ti-O-N) and interstitial nitrogen (O-Ti-N). Silver species could be in the form of Ag0 and Ag2O. The photocatalytic performance of the photocatalysts coated on stainless steel mesh was investigated by the degradation of aqueous MB and gas phase NH3 under visible LED light illumination for three recycling runs. The highest photocatalytic activity and recyclability were reached in 5% N/Ag-TiO2 showing the efficiency of 98.82% for methylene blue (MB) dye degradation and 37.5% for NH3 removal in 6 h, which was 2.7 and 4.3 times, respectively. This is greater than that of pure TiO2. This was due to the synergistic effect of N and Ag doping.

Photocatalysis for Air Treatment Processes: Current Technologies and Future Applications for the Removal of Organic Pollutants and Viruses

“…However, by impregnating, doping, or co-doping TiO 2 with metals such as iron (Fe), silver (Ag), palladium (Pd) and platinum (Pt) or non-metals like nitrogen (N), one can improve (a) the reduction of the TiO 2 energy band gap (E BG < 3.2 eV), (b) the slowing of the (e − )/(h + ) recombination rate, and (c) the diminishing of the particle agglomeration [17,18]. Furthermore, through the use of a new photocatalyst synthesis utilizing a sol-gel method, larger TiO 2 surface areas (50 m 2 /g < S BET ≤ 150 m 2 /g), morphologies (high porosity) and crystal structures (anatase dominant crystalline phase) can be obtained [11,19]. All these advancements with TiO 2 photocatalysts are extremely important for the improvement of the process of photocatalysis and the extensive application of air treatment, both for VOCs conversion and airborne virus inactivation.…”

“…During the past few years, numerous photoreactor configurations for PCO (Photocatalytic Oxidation) have been reported in the literature, including fixed-bed reactors [20][21][22], fluidized-bed reactors [23,24], coated honeycomb monolith reactors [25][26][27], fixed powder layer reactors [28,29], annular coated reactors [11,30], and annular mesh-coated Venturi-reactors [2,12,13]. These reactor configurations are relevant given that they determine the PCO process.…”

“…This method appears to enhance the photocatalytic activity of single-and co-doped TiO 2 (anatase) under both UV and sunlight irradiation for toluene degradation [59]. Sirivallop et al (2020) employed an in-situ solvothermal method to prepare four different photocatalysts: (1) TiO 2 , (2) N-doped TiO 2 , (3) Ag-doped TiO 2 and (4) N/Ag co-doped TiO 2 . This resulted in more effective photocatalytic materials for the degradation of gaseous ammonia (NH 3 ) under visible light-emitting diode (LED) irradiation [11].…”

“…Sirivallop et al (2020) employed an in-situ solvothermal method to prepare four different photocatalysts: (1) TiO 2 , (2) N-doped TiO 2 , (3) Ag-doped TiO 2 and (4) N/Ag co-doped TiO 2 . This resulted in more effective photocatalytic materials for the degradation of gaseous ammonia (NH 3 ) under visible light-emitting diode (LED) irradiation [11]. Similarly, Yang et al (2010) prepared a series of N-doped anatase TiO 2 photocatalysts active under visible light [72].…”

Solar-Powered Photodegradation of Pollutant Dyes Using Silver-Embedded Porous TiO2 Nanofibers

“…The huge band gap of TiO 2 (E g = 3.2 eV for anatase and 3.0 eV for rutile) restricts its absorption of electromagnetic radiation only to the UV region. Doping of the semiconductor could narrow the band gap for visible light absorption [ 13 ]. Alternatively, the presence of complementary noble metal nanoparticles (NPs) could supplement the semiconductor in absorbing visible light atop of strengthened UV radiation absorption.…”